This invention relates to internal combustion engines, and in particular, to an improved throttle structure for controlling fluid passage to the combustion chambers during the intake stroke of the engine.
In the design of internal combustion engines prevalent today, the combustion chambers of the engine are connected to a source of fuel and a source of air through an intake manifold and a carburetor. The carburetor has a main air passageway extending through it, and a venturi restriction is used to draw fuel into the air stream. Control of the flow through the passageway is obtained through use of a throttle valve.
Throttle valves conventionally have included a rotatable plate positioned in the air passageway of the carburetor, downstream of the carburetor venturi. The plate commonly is rotatable between a closed position in which the plate substantially blocks passage of the fuel/air mixture through the carburetor, and an open position which permits passage of fluid past the throttle plate. The carburetor itself usually is positioned above the engine intake manifold. The manifold contains a plurality of passages which are operatively connected to the air passage of the carburetor on one end, and with the combustion chambers of the engine on another end.
It long has been known that the combustion chambers of an engine receive varying amounts of fuel during operation of the engine. Ideally, each intake stroke of the piston would draw a fuel/air mixture into a particular combustion chamber which would burn completely during the power stroke of the piston. In fact, various ones of the engine chambers receive a fluid mixture during intake which varies between each of the combustion chambers in a particular cycle and between individual combustion chambers during different cycles. The reasons for unequal distribution also generally are known. Thus, when fuel and air strike a conventional throttle valve, large droplets of fuel often are formed. Large fuel droplets do not move readily to the combustion chambers, and distort the fuel/air mixture ratio when they do finally arrive. Since the throttle valve commonly is pivotally mounted across the diameter of the carburetor air passage, fluid movement past the throttle is unbalanced or directed toward one side or the other of the air passage. Proper balance is rarely achieved.
The unequal fluid distribution provided by conventional manifold-carburetor constructions is known to reduce the fuel economy of the engine, and to make control of engine pollutants a difficult process. That is to say, control of pollutants in the exhaust of the engine is complicated by the fact that the amount of pollutants varies because of the efficiency or non-efficiency of the power stroke of the engine. In turn, the efficiency depends at least in part on the fuel/air mixture present in the combustion chamber at combustion.
A number of attempts have been made to improve the consistency of the air/fuel mixture delivered to the cylinders of an internal combustion engine. In general, prior art attempts have involved complicated redesigns of the fuel/air delivery system, for example, by the use of fuel injection mechanisms, or complicated redesigns of the engine. While such systems and redesigns work for their intended purposes, they are expensive to produce. Fuel injection mechanisms also are expensive to maintain in normal operational use.
The invention disclosed hereinafter is an improved throttle structure for a conventional carburetor, which may be implemented with little change in carburetor design. Related inventions are disclosed in a copending application by Edward H. Casey, "Means for Imparting Supersonic Flow Characteristics in the Intake Manifold of an Internal Combustion Engine", (Ser. No. 727,719, filed 9/29/76, and a copending application by Donald L. Hicks and Richard D. Doerr, "Throttle Structure for Imparting Supersonic Flow Characteristics in the Intake Manifold of an Internal Combustion Engine", Ser. No. 727,718, filed 9/29/76, assigned to the Assignee of the present invention. Information disclosed in these copending applications is intended to be incorporated by reference. As described more fully hereinafter, the incoming fuel and air mixture, in one embodiment, is permitted to strike the bottom wall of the intake manifold of the engine. A throttle structure, in conjunction with the bottom wall, is utilized to regulate engine demand with fluid flow. The throttle structure permits uniform distribution of the mixture through the intake manifold to an extent heretofore impossible with plate-type throttle valves of the prior art.
One of the objects of this invention is to provide a throttle structure for an internal combustion engine which gives better fuel/air mixture distribution to the cylinders of the engine.
Another object of this invention is to provide a throttle valve structure having an inlet side and an outlet side, the outlet side being positioned in the inlet manifold of an internal combustion engine.
Another object of this invention is to provide a throttle valve structure which utilizes a tubular body member as the valve element.
Yet another object of this invention is to provide a throttle structure which permits heating of the fuel/air mixture prior to fuel/air mixture entrance into the combustion chambers of the engine.
Still another object of this invention is to provide a throttle structure for an internal combustion engine giving improved fuel/air mixture distribution without requiring major design changes in either the carburetor or the intake manifold of the engine.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.